I have an expensive, reliable Dinotte. (But it's very wide beam wouldn't be ideal for a fast e-bike. A narrower beam would reach farther down the road. The Dinotte beam is very smooth, with a gradual fade at the edges. I like it.)
For an e-bike commute, I'd buy two no-name lights. These lights often greatly exaggerate their lumens, so assume the lumens are likely 50% or less of the stated number. It'll still be quite bright. I've never seen these in person, but I assume the beam will have hot spots and/or sharp edge cutoffs. Two lights might help even it out, though.
Two lights, for backup in case of a light failure. And to have two separate beams lighting up the road for better coverage.
Crank them up to max around sunset -- that can be a dangerous time of day. Then run at the medium after dark.
Lithium batteries seem to last just a few years before having a reduced run time. It's best to store them long term with a partial charge, maybe 2/3 to 3/4 charge, and keep in a cool place.
Last edited by rm -rf; 11-06-18 at 07:43 AM.